Federal standards in the United States prescribe characteristics of seat and restraint systems in transport category airplanes during emergency landing conditions. Among requirements of U.S. regulations is that “each seat type design approved for crew or passenger occupancy during takeoff and landing must successfully complete dynamic tests or be demonstrated by rational analysis based on dynamic tests of a similar type seat” pursuant to certain parameters thereafter provided. See 14 C.F.R. § 25.562. Accordingly, sections of tracks to which aircraft seats are connected must be mounted to test fixtures for purposes of performing the required dynamic testing.
Aircraft seat tracks conventionally comprise a horizontally-oriented base plate from which a crown upwardly extends. The base plate is connected to a structural member of the air frame of the aircraft in which it is situated to prevent relative movement of the plate and frame. Passenger or crew seats (or both) are connected to the crowns of the tracks. Such connection may be direct or indirect and need not necessarily be permanent, as many aircraft cabins are reconfigured from time to time.
FIGS. 1A-C illustrate a section of seat track 10 as conventionally used for testing purposes. As is typical, track 10 includes base plate 14 as well as integrally-formed crown 18. Crown 18 extends longitudinally along base plate 14 and is symmetric about a longitudinally-extending center line CL of the plate 14. For conventional testing purposes, also created within track 10 are multiple through holes 22 longitudinally spaced along base plate 14 in the region of crown 18. Holes 22 are centered transversely in base plate 14; i.e. they are aligned with center line CL.
Also detailed in FIG. 1A are load cell 26 and mounting interface 30. Load cell 26 forms part of a dynamic test fixture for seat track 10 pursuant to federal standards. As illustrated, upper surface 34 of load cell 26 typically has circular cross-section with (four) mounting openings 38 spaced ninety degrees about its periphery.
Mounting interface 30 functions to facilitate connection of seat track 10 to load cell 26. Interface 30 conventionally comprises a structure of generally-rectangular cross-section with two sets of openings 42 and 46, one each to match holes 22 and openings 38. Openings 46 extend through interface 30 in alignment with openings 38 of load cell 26. Consequently, bolts or other fasteners may be passed through openings 46 into openings 38 to attach interface 30 to load cell 26.
Openings 42, by contrast, are designed to align with holes 22. They thus are spaced longitudinally in a central region 50 of interface 30 and accept bolts 54 (or other fasteners) passed through holes 22 to connect track 10 and interface 30. Because bolts 54 do not extend into load cell 26, openings 42 need not necessarily extend the full depth of interface 30.
At least a substantial portion of upper surface 58 of interface 30, as well as lower surface 62 of base plate 14, are flat, so that most or all of upper surface 58 is available to support the plate 14 when interface 30 and plate 14 are connected. Likewise, both lower surface 66 of interface 30 and upper surface 34 of load cell 26 are flat. Accordingly, interface 30 and plate 14 readily rest upon load cell 26 during testing.
In some cases it may be beneficial to test seat tracks more representative of those actually installed in aircraft. FIGS. 2A-B depict, among other things, one such seat track 70. Like seat track 10, track 70 includes a (flat) base plate 14. Track 70 additionally comprises an integrally-formed crown 18 extending longitudinally therealong and which is symmetric about a longitudinally-extending center line CL of the plate 14. Unlike track 10, seat track 70 also includes a vertical member 74 extending downward from plate 14 along center line CL, thus assuming a “T” shape in cross-section. Alternatively, seat track 70 may include both vertical member 74 and a horizontal base member 222 (see, e.g., FIG. 3D) so that it assumes an “I” shape in cross-section.
The presence of vertical member 74 precludes ready attachment of track 70 to interface 30, as lower surface 62 of base plate 14 no longer may abut upper surface 58 of the interface 30. The existence of vertical member 74 thus likewise disrupts creation of holes 22. Accordingly, new mounting techniques and systems must be devised to perform dynamic testing of track 70 to comply with federal regulations.